Whiteside, projected to be Miami's starter, will miss his second consecutive exhibition game Wednesday when the Heat face the Orlando Magic in Louisville, Kentucky.
The team continues to officially list Whiteside as day-to-day, but he has yet to practice since training camp opened last week.
"It'll be maybe a week or maybe more," Whiteside said after Tuesday's practice at AmericanAirlines Arena. "It really is just day-to-day at this point. I expect to play before the season starts. Hopefully, I can catch a couple of these preseason games before the season starts, to get out there with the team."
Last season, Whiteside became the first NBA player in more than 50 years to average at least 11.8 points, 10.1 rebounds and 2.6 blocks in less than 24 minutes a game. He finished fourth in voting for the NBA's Most Improved Player award after he was signed in December following a stint in the NBA Development League.
Heat coach Erik Spoelstra said Whiteside would travel with the team to Louisville, but only to continue his conditioning and rehab work with the training staff.
After injuries ravaged the roster during last season's 37-45 finish, the Heat were optimistic about entering camp this month healthy and with their projected starting group of Goran Dragic, Dwyane Wade, Luol Deng, Chris Bosh and Whiteside intact.
But Whiteside sustained the injury during a conditioning workout three days before the start of camp, when he said he felt "a tug" on his calf. Since then, the promising 7-footer has been relegated to free throws on the side courts at practice and exercises on the stationary bike, treadmill or in the pool between the workouts.
"He's making progress, but he's still not ready to practice," Spoelstra said. "Until he's ready to practice, I'll focus on the guys we have out here."
Veteran center Amar'e Stoudemire, signed by the Heat to a one-year deal for the $1.6 veteran's minimum, is expected to get significantly more playing time in the preseason until Whiteside returns. Stoudemire finished with 12 points and six rebounds in 16 minutes off the bench in Sunday's loss to Charlotte in the Heat's preseason opener.
Whiteside said it's been tough to sit out but that he can't afford rush back and risk further damage.
"I never strained anything so I really didn't know what was going on," Whiteside said. "They said it's something you have to really be careful with and not try to rush through it. It's tough [to watch games], but I get on a bike and watch practice and try to stay in shape a little bit. That's the toughest part, just knowing you have to come back in shape. It's going to take a little bit of time, but not too long."